I have been away from the yacht for 3 months & left my 15HP Yammy on the back of the tender in the tilt position. I figured it had enough downward tilt to drain & be fine. It now appears to have seized. I cannot pull the cord & cannot turn the prop when the engine is in gear. (I usually can with abit of effort) Any suggestions about what may have happened? Could this be a bottom bearing seizure or worse? Where can I purchase a workshop manual for this motor circa approx. 2007?
Thanks

If it is the cylinder that has siezed, start by rocking the flywheel back and forth. Your trying to work the rings loose, don't apply much force at first, try rocking it and letting the oil into the ring lands to loosen things up, you can usually tell if a piston has seized as there is some play in the crankshaft, if the crank has seized (unlikely) then there will be no movement at all in the flywheel

Yup like others have said let it soak, even a day is good, might have to remove the pull cord assembly and put a socket on the flywheel to loosen up, like the other OP state, work it back and forth. I would not do that with trying to turn the prop.

Oops...
If it was left without any preventative maintenance it is going to be damaged.

Be very very gentle when you start rocking it loose. Also, remove the carb and the reed valve cage. You will be able to see the big-end bearings. The center main, upper and lower bearings will also be accessible. You will be able to see the crankshaft and judge the condition.

The Enduro is supposed to run on 50:1 oil mix, and its the same bearings as the Leisure model that is 100:1. If you were running 50:1 of TCW3 grade oil you could be OK.

Best case, you slowly rock it free and it runs for another year or two, but it will be rough. Many of these have recovered like this, but they never sound great again.

Worst case, its a new crankshaft assembly with bearings.

It is possible to push the center bearing pin out and replace the CM bearing, but, in my experience, the push fit is a one time deal, a re-fit can work but you run the risk of both big end journals wanting to be next to each other not 180 degrees apart.

To remove the carb.
Remove the stop lanyard.
Remove two screws and remove the plastic resonator. Remove fuel hose using a long or needle nose pliers. Disconnect the choke linkage by rotating the white plastic catch and then withdraw the Stainless Steel linkage. Loosen the throttle linkage set screw, and then put motor in gear and open the throttle, the link will fall out. Place back in N. Undo the two 10mm bolts and withdraw the carb. Remove the small hose on the reed cage. (This is a reverse pulse hose to snap the reed shut) Undo the 3 x 10mm monel bolts and withdraw the reed cage using the slots provided to lever it with a flat screwdriver. Inspect reed valves and retainers for rust.

Use a flashlight and inspect the crankshaft and bearings.

Use 50/50 mix of kerosene or diesel and TCW3 outboard oil to liberally and I mean LIBERALLY rinse the entire mechanism while rocking it free. You need to allow it to rinse the rust away from the journals and not allow the rust flakes to re-attach in a good area. I use a spray bottle and approx a quart of liquid. It will drain out of the exhaustports, place a receptacle under the prop.

While doing the above, of course spray into the spark plug holes as well.

No tools are required to add the force required, if you cant do it by hand, do not add torque. Its easier to remove the start cowl by loosening 3x 10mm monel bolts, and you can leave it hanging on the "In gear start protect cable"

When you get it started again, treat as for running in a new motor, details in owners manual.

I am overwhelmed! Many thanks to all for your excellent advice & thank you Gordmay for your welcome to the fold.
Right now all the important little bits are marinating in a good vintage penetrating oil. Will do more tomorrow & keep you all up to speed with hopeful progress.
Tommee

That"s pretty interesting. What part of the crankshaft can you see? How many times have you done this?

You can see Cyls 1 and 2 big end, and the counterweights, and you can see up into the skirt of the pistons. You can just see the bottom Crankshaft main bearing. You can guess the Center main and top with an extension tube on a spray can. If you have a borescope you can see everything.

Yippee........Yahoo........Yeah!!!! She runs like a good un, Thank you team.
After soaking for 24 hrs the flywheel took very little effort to turn with a socket. I turned it back & forth by hand for a while until is was really smooth. Replaced the spark plugs & cowling & tried to start it. Took a while for it to fire but away it went & runs like a sewing machine again. Guess I was lucky & got away with it this time. Thank you all for your input.
Must admit I did fog my last outboard, a 15hp Mariner, the grunty version probably equivalent to the enduro. It was 7 years old when I had the chance to go away for 6 months & I meticulously fogged it with the correct stuff etc. It never ran well again after that. I had it another 10 years put it was a pig to start, ran rough, stalled on idle & even after an expensive trip to the doctors, ran even worse!!!! Rather put me off this practice.
Anyway, many thanks again....happy sailing to all